I. Field of the Invention
This invention relates generally to a stabilizer system for a recreational vehicle, such as a four-wheeled, soft tire vehicle or a snowmobile, where the vehicle is equipped with a torsion bar or other spring-type stabilizer, and more particularly to control mechanisms for increasing the effective spring rate of the outside wheel or ski during cornering maneuvers to thereby decrease the sway of the vehicle due to centrifugal force.
II. Discussion of the Prior Art
In a co-pending application of Gregory J. Marier filed concurrently herewith (U.S. Pat. No. 4,593,921, issued June 10, 1986) and entitled "Stabilizer System For A Snowmobile", there is described a means of adjusting the "stiffness" of a suspension system of the type incorporating a shock absorber having an air cushion such that the outside ski of the vehicle exhibits a relatively high spring constant as compared to the inside ski during a turning maneuver. As is explained in the aforereferenced Marier patent application, snowmobiles and the popular off-road wheeled vehicles having the large, low pressure tires are generally designed to have a large vertical excursion of the wheel or ski, upon hitting an irregularity in the terrain. A partial solution to the roll or sway problem occasioned by such a suspension system has centered around the incorporation of a torsion bar. The conventional manner of applying a torsion bar to a snowmobile-type vehicle is set out in the Yasui et al U.S. Pat. No. 4,372,567. When the snowmobile in accordance with the Yasui et al patent is traversing a straight-line path, the torsion bar helps suppress shock and vibration. This arrangement has a drawback in that if, while negotiating a turn, the inside ski encounters a bump, the anti-sway force exerted by the stabilizer bar upon the outside ski is interrupted and the vehicle handling characteristics are changed suddenly.
The present invention describes a method and apparatus for obviating the foregoing problem. A control apparatus is coupled to the torsion bar or spring-type stabilizer so as to increase the effective stiffness or spring rate of the suspension of the outside wheel or ski as the vehicle negotiates a turn while, at the same time, decoupling the stabilizer system from the inside ski or wheel so that it is free to operate independently. Thus, even if a bump is encountered during a cornering maneuver, there are no sudden handling changes but, in fact, the vehicle exhibits a steady reistance to swaying throughout the full maneuver.